In fuel systems of internal combustion engines, fuel pumps are used for transporting fuel. In systems with direct petrol injection, the fuel pumps are supplemented by high-pressure fuel pumps which compress the fuel, supplied for example by an electric fuel pump at a pre-pressure, in sufficient quantities to the level necessary for the high-pressure petrol injection.
Such fuel pumps usually have at least one piston which can be moved axially by means of a drive formed by a cam or an eccentric disk. A necessary return force of the piston is generated by means of a compression spring. For example, a spring plate pressurized by a compression spring is pressed onto an end portion of the piston. A piston seal, arranged radially outward on the piston, can separate a first fuel-side portion of the piston from a second oil-side portion of the piston, which keeps mixing of fuel and oil at least to a low level. One such piston seal, also called a low-pressure seal, is normally held by a holding device, also known as a seal carrier. The seal carrier is connected to the housing of the high-pressure fuel pump such that here too, the oil-side portion of the fuel pump is reliably sealed from a fuel-side portion, wherein the seal carrier constitutes a static seal against the low-pressure seal and against the housing.
The seal carriers are for example made from deep-drawn elements which undergo a substance-bonding to the housing of the high-pressure fuel pump by means of a laser weld seam, and thus provide a static seal between the oil and fuel sides.